CN109182640B - Method for reducing carbon oxygen deposit at smelting end point of converter - Google Patents
Method for reducing carbon oxygen deposit at smelting end point of converter Download PDFInfo
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- CN109182640B CN109182640B CN201811101957.XA CN201811101957A CN109182640B CN 109182640 B CN109182640 B CN 109182640B CN 201811101957 A CN201811101957 A CN 201811101957A CN 109182640 B CN109182640 B CN 109182640B
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- converter
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- oxygen
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
Abstract
A method for reducing carbon-oxygen deposit at the end point of converter smelting is characterized by adding crushed magnesia-carbon bricks and a catalyst into a converter when the temperature of molten steel is more than or equal to 1500 ℃ at the middle and later stages of converter smelting, wherein the magnesium isThe carbon brick is derived from magnesia carbon brick discarded by replacing new brick after the expiration of furnace service or the offline of a ladle, and the catalyst is derived from fluorite. By adopting the method, the carbon-oxygen product at the smelting end point of the converter is from 0.27 to 10‑6～0.32*10‑6Down to 0.18 x 10‑6～0.22*10‑6The content of [ O ] in the steel is reduced from 0.07-0.08% to 0.03-0.05%. For aluminum killed steel, the content of [ O ] in the steel is averagely reduced by 0.03 percent, 1.15kg/t of aluminum alloy can be saved, the price of the aluminum alloy is calculated according to 1.2 ten thousand yuan/t, and the production cost is reduced by 13.8 yuan/t. In addition, MgO produced by combining MgO which is not completely reduced with Mg and O enters the slag to carry out slag splashing and furnace protection to maintain the furnace condition.
Description
Technical Field
The invention relates to a steel smelting method, in particular to a method for reducing carbon and oxygen deposit at the smelting end point of a converter.
Background
Under the working condition of a converter, C and O dissolved in molten steel have a certain fixed product, and the premise is that under the condition that the partial pressure and the temperature of the carbon content are fixed, the C-O reaction relation can be utilized, namely m is omega [ C [ ]]×ω[O]At equilibrium (certain temperature T and equilibrium partial pressure P)CO) Is a constant. According to the principle of reaction equilibrium, the mass fraction of oxygen is increased with the decrease of carbon in steel, so that the end point carbon-oxygen volume of molten steel is an important basis for balancing oxygen in steel. In the tapping process, the mass fraction of oxygen in molten steel can be reduced as much as possible while a certain mass fraction of carbon is ensured, so that the reduction of the end point carbon-oxygen deposit of the converter is beneficial to reducing the alloy consumption, reducing inclusions formed in the deoxidation process and improving the quality of the molten steel, and has important significance for reducing the steelmaking cost and producing high-quality products.
After the blowing of the traditional converter enters the final stage, because the carbon content in the molten pool is greatly reduced and the decarburization reaction is weakened, most of the oxygen blown into the molten pool reacts with the iron in the molten steel or is directly dissolved in the molten steel, the oxidizability of the slag is greatly improved and the dissolved oxygen in the molten steel is rapidly increased. For smelting low-carbon steel, the carbon-oxygen deposit at the end point of the combined blown converter is more than 0.26 x 10-6～0.28×10-6In a top-blown converter at 0.28X 10-6～0.30×10-6And sometimes even greater than 0.35X 10-6Far above the theoretical equilibrium value of 0.25X 10-6. The direct consequence of this peroxidation is, on the one hand, an increase in the amount of deoxidation alloy, i.e. an increase in the production costs, and, on the other hand, a considerable increase in the difficulty of controlling the purification of the steel.
Disclosure of Invention
The invention provides a method for reducing the carbon oxygen deposit at the smelting end point of a converter, which is characterized in that waste magnesia carbon bricks and a catalyst are added into the converter at the middle and later stages of the converter blowing, so that the aim of reducing the carbon oxygen deposit at the smelting end point of the converter is fulfilled.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for reducing carbon and oxygen deposits at the smelting end point of a converter is characterized in that when the temperature of molten steel in the middle and later stages of the converter smelting is more than or equal to 1500 ℃, crushed magnesia carbon bricks and a catalyst are added into the converter through a high-level bunker, the magnesia carbon bricks are derived from magnesia carbon bricks discarded by replacing new bricks after the service of the converter expires or steel ladles are taken off line, and the catalyst is derived from fluorite.
According to the method for reducing the carbon-oxygen deposit at the smelting end point of the converter, the adding amount of the magnesia carbon bricks is 1.1-1.2kg per ton of steel, and the adding amount of fluorite is 20 percent of the adding amount of the magnesia carbon bricks.
According to the method for reducing the carbon-oxygen deposit at the smelting end point of the converter, the magnesia carbon brick comprises the following components: 78-82% of MgO, 9-11% of C and the balance of CaO and SiO2、Al2O3Combined slag of oxides.
According to the method for reducing the carbon-oxygen deposit at the smelting end point of the converter, the crushed particle size of the magnesia carbon brick fed into the converter is 20-50 mm.
In the method for reducing the carbon-oxygen deposit at the smelting end point of the converter, the adding time of the magnesia carbon bricks and the catalyst is 0.68-0.72 of the total oxygen supply time.
In the method, waste magnesia carbon bricks and fluorite are added from a high-position storage bin in the middle and later stages of converter blowing, C in steel and C in magnesia carbon bricks are used as reducing agents and fluorite is used as a catalyst at the high temperature of 1500 ℃, MgO in the magnesia bricks is reduced into Mg and CO, and Mg and steel produced by reduction reaction [ (Mg and steel ]The O reaction reduces [ O ] in the steel, and the reduction of CO reduces P in the gas phaseCOThereby achieving the purpose of reducing the carbon-oxygen deposit at the smelting end point of the converter. By adopting the method, the carbon-oxygen product at the smelting end point of the converter is from 0.27 to 10-6～0.32*10-6Down to 0.18 x 10-6～0.22*10-6The content of [ O ] in the steel is reduced from 0.07-0.08% to 0.03-0.05%. For aluminum killed steel, the content of [ O ] in the steel is averagely reduced by 0.03 percent, 1.15kg/t of aluminum alloy can be saved, the price of the aluminum alloy is calculated according to 1.2 ten thousand yuan/t, and the production cost is reduced by 13.8 yuan/t. In addition, MgO produced by combining MgO which is not completely reduced with Mg and O enters the slag to carry out slag splashing and furnace protection to maintain the furnace condition.
Detailed Description
The mechanism of action and the method of implementation of the invention are detailed below:
1. the chemical formula of the decarbonization reaction in the molten pool of the converter is 1: [ C ] + [ O ] ═ CO
Formula 1: kc ═ Pco/(a [ C ]. a [ O ]) ═ Pco/(fc [% C ]. fo [% O ])
In the formula 1, KCIs an equilibrium constant that is temperature dependent only; pCOIs the partial pressure of CO; a [ C ]]And a [ O ]]The activity of carbon and oxygen in the molten steel respectively; f. ofCAnd fOThe activity coefficients of carbon and oxygen in the molten steel are respectively [% C]When the content is less than or equal to 2.00 percent, fC×fO1, so that:
formula 2: kc ═ Pco/(a [ C ]. a [ O ]) [% C ]. C [% O ]
Carbon oxygen product [% C ] · [% O ] ═ Pco/Kc
The factors influencing the end point carbon oxygen deposit when the reaction reaches the equilibrium are Kc and PCO、[％C]、[％O]Kc is a constant that is only related to temperature, so the factors that affect the end point carbon oxygen product when the reaction reaches equilibrium are: temperature (T), PCO、[％C]、[％O]I.e. P at equilibriumCO、[％C]、[％O]The lower the carbon oxygen deposit, the higher the temperature (T) and the lower the carbon oxygen deposit. Therefore, the P content in the steel is reduced while the temperature (T) is kept constantCO、[％C]、[％O]The aim of reducing the carbon-oxygen deposit at the end point of the converter can be achieved.
2. The wall and ladle of converter are made of refractory magnesia carbon bricksThe magnesia carbon bricks are laid, after the campaign expires or the ladle is taken off line, the magnesia carbon bricks are eroded and thinned, new bricks need to be replaced, the waste magnesia carbon bricks mainly comprise MgO and C, the MgO content is about 80 percent, the C content is about 10 percent, and the other components are CaO and SiO2、Al2O3And the like. Before the magnesia carbon bricks are used, the magnesia carbon bricks are crushed into 20-50mm granularity for standby, the magnesia carbon bricks with the granularity smaller than 20mm are blown from the bottom and stirred to float to a slag layer without being reduced in the converter, and the magnesia carbon bricks with the granularity larger than 50mm are not completely reduced in the converter within 3-5 min.
The temperature of molten steel in the middle and later periods of smelting in the converter reaches more than 1500 ℃, at the moment, crushed magnesia carbon bricks are added through a high-level bunker, reducing agents are C in steel and C in magnesia carbon bricks, and a catalyst is fluorite (the main component of fluorite is CaF)2). Coke and fluorite are also added from the overhead bin with the magnesia carbon bricks. Fluorite CaF2Belongs to non-surface active substance, can increase the reaction energy of the oxide surface and improve the reaction activity of the oxide. When carbon reduces magnesium oxide, part of F-ions in unsaturated bonds and unsaturated energy have higher activity, and the part of F-ions with higher activity can penetrate into MgO crystals to influence the lattice structure, increase the lattice distortion of magnesium oxide, promote the damage of the MgO crystal structure and break Mg-O bonds, so that the unsaturated bonds are generated on the surface of magnesium oxide, the reaction energy is increased, the reaction activity is improved, and the reduction reaction is accelerated.
The reduction reaction that takes place in the converter is as follows:
mg + O → MgO … … … … … … … … … … … chemical formula 3
3. MgO is reduced into Mg by carbon under the action of a fluorite catalyst, the Mg is an element with strong oxidizability, the Mg generated by the reaction is converted into MgO when meeting O in steel, the O in the steel is continuously reduced along with the reduction reaction, and the reduction reaction is promoted by the conversion of the Mg and the O into the MgO. The chemical reaction generated in the period from the middle and later stages of the converter smelting to the smelting end point for about 4min continuously reduces the contents [ C ] and [ O ] of the steel, so thatThe amount of carbon and oxygen is reduced at the end of the converter, i.e. at equilibrium. Simultaneously, the bottom blowing argon flow in the later stage of converter smelting is 80-100m3And h, under the action of the large-flow bottom blowing, CO generated by the reduction reaction is quickly recovered along with the furnace gas. The flow of bottom-blown argon is less than 80m3During the reaction, the stirring force of the gas on the molten steel is insufficient, so that CO can not be rapidly recovered along with the furnace gas; the flow of bottom-blown argon is more than 100m3At the hour, the molten steel is seriously overturned, and the molten steel is exposed and is easy to oxidize.
4. The relation between the amount of MgO to be added and the amount of [ C ], [ O ] in the reduced steel [ (C ], [ 0.3 [% MgO ]), calculated by chemical equations of chemical formula 2 and chemical formula 3; (% O) (% MgO) (% C) (% O) (% 0.12) (% MgO)2. To reduce the carbon-oxygen product by 0.09 x 10-6，〔％MgO〕2＝0.75*10-6Calculated [ (MgO) ] about 0.875X 10-3The magnesia carbon brick contains about 80 percent of MgO, and the magnesia carbon brick added per ton of steel comprises the following components: 0.875*10-3And/0.8 equals 1.1 kg. In the actual production process, the granularity is 20-50mm, the condition that the granularity is less than 20mm is stirred to a slag layer by bottom blowing argon due to collision exists during blanking from a high-level bunker, the condition accounts for 10 percent through field large-scale data statistical analysis, and the adding amount of magnesia carbon bricks to a ton of steel is 1.1-1.2 kg. The adding amount of fluorite is 20 percent of the adding amount of magnesia carbon bricks, namely the adding amount of steel per ton is 0.22kg, the data is obtained through multiple tests and comparison, when the adding amount of fluorite per ton steel is more than 0.22kg, converter slag is thinned, slag cannot be hung on a furnace wall during slag splashing furnace protection, the furnace protection effect cannot be achieved, and when the adding amount of fluorite per ton steel is less than 0.22kg, the catalysis effect cannot be achieved, and the purpose of reducing carbon and oxygen products cannot be achieved.
By adopting the technology, the carbon-oxygen product at the smelting end point of the converter is from 0.27 to 10-6～0.32*10-6Down to 0.18 x 10-6～0.22*10-6The content of [ O ] in the steel is reduced from 0.07-0.08% to 0.03-0.05%. For aluminum killed steel, the content of [ O ] in the steel is averagely reduced by 0.03 percent, 1.15kg/t of aluminum alloy can be saved, the price of the aluminum alloy is calculated according to 1.2 ten thousand yuan/t, and the production cost is reduced by 13.8 yuan/t. In addition, MgO produced by combining MgO which is not completely reduced with Mg and O enters the slag to carry out slag splashing and furnace protection to maintain the furnace condition.
Several specific embodiments of the invention are provided below:
example 1: making steel in a 100T converter, wherein the C content of the charged molten iron is 4.5 percent, the charging temperature of the molten iron is 1400 ℃, adding the molten iron into the converter for smelting, the total oxygen supply time is 14min, 110kg of magnesia carbon brick and 22kg of fluorite are added from a high-level storage bin when oxygen is supplied for 10min, and the flow of bottom-blown argon is 100m3The end temperature of the converter is 1630 ℃, the carbon content of the molten steel is 0.05 percent, the oxygen content is 0.036 percent, and the carbon-oxygen product is 0.18 to 10-6。
Example 2: making steel in a 100T converter, wherein the C content of the charged molten iron is 4.5 percent, the charging temperature of the molten iron is 1400 ℃, adding the molten iron into the converter for smelting, the total oxygen supply time is 15min, 120kg of magnesia-carbon brick and 24kg of fluorite are added from a high-level storage bin when oxygen is supplied for 10.5min, and the bottom blowing argon flow is 80m3The end temperature of the converter is 1630 ℃, the carbon content of the molten steel is 0.055%, the oxygen content is 0.04%, and the carbon-oxygen product is 0.22 x 10-6。
Example 3: making steel in a 100T converter, wherein the C content of the charged molten iron is 4.5 percent, the charging temperature of the molten iron is 1400 ℃, adding the molten iron into the converter for smelting, the total oxygen supply time is 14min, 115kg of magnesia-carbon brick and 23kg of fluorite are added from a high-level storage bin when oxygen is supplied for 10.5min, and the bottom blowing argon flow is 90m3The end temperature of the converter is 1630 ℃, the carbon content of the molten steel is 0.05 percent, the oxygen content is 0.04 percent, and the carbon oxygen product is 0.2 to 10-6。
Comparative example: making steel in a 100T converter, wherein the C content of the charged molten iron is 4.5 percent, the charging temperature of the molten iron is 1400 ℃, the molten iron is added into the converter for smelting, the total oxygen supply time is 14min, and the bottom blowing argon flow is 70m3The end temperature of the converter is 1630 ℃, the carbon content of the molten steel is 0.04%, the oxygen content is 0.07%, and the carbon oxygen product is 0.28 to 10-6。
As can be seen from the above examples and comparative examples, the process of the present invention can significantly reduce carbon oxygen deposition.
Claims (4)
1. A method for reducing carbon and oxygen deposit at the smelting end point of a converter is characterized by comprising the following steps: adding crushed magnesia carbon bricks and a catalyst into a converter through a high-level bunker when the temperature of molten steel is more than or equal to 1500 ℃ in the middle and later smelting periods of the converter, wherein the magnesia carbon bricks are derived from magnesia carbon bricks discarded by replacing new bricks after the service of the converter expires or a ladle is taken off line, and the catalyst is derived from fluorite; the adding amount of the magnesia carbon brick is 1.1-1.2kg per ton of steel, and the adding amount of the fluorite is 20 percent of the adding amount of the magnesia carbon brick.
2. The method for reducing the carbon oxygen deposit at the end point of converter smelting according to claim 1, which is characterized by comprising the following steps: the magnesia carbon brick comprises the following components: 78-82% of MgO, 9-11% of C and the balance of CaO and SiO2、Al2O3Combined slag of oxides.
3. The method for reducing the carbon oxygen deposit at the end point of converter smelting according to claim 2, characterized in that: the crushed particle size of the magnesia carbon brick charged into the furnace is 20-50 mm.
4. The method for reducing the carbon oxygen deposit at the end point of converter smelting according to claim 3, characterized in that: the adding time of the magnesia carbon brick and the catalyst is 0.68-0.72 of the total oxygen supply time.
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| CN109825664A (en) * | 2019-04-12 | 2019-05-31 | 攀钢集团攀枝花钢铁研究院有限公司 | The method for reducing converter terminal molten steel carbon oxygen product |
| CN109825665B (en) * | 2019-04-12 | 2020-09-25 | 攀钢集团攀枝花钢铁研究院有限公司 | Method for reducing carbon and oxygen deposit of molten steel at converter end point |
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| JPS591610A (en) * | 1982-05-28 | 1984-01-07 | Shinagawa Rozai Kk | Composite slag forming agent for basic steel making furnace |
| CN101177723A (en) * | 2007-11-27 | 2008-05-14 | 中冶华天工程技术有限公司 | Method for controlling concentration of oxygen in molten steel |
| CN103451373B (en) * | 2013-09-18 | 2015-02-18 | 新疆中合大正商贸有限公司 | Magnesium ball used for converter steelmaking and production technology thereof |
| CN108018398A (en) * | 2016-10-28 | 2018-05-11 | 上海梅山钢铁股份有限公司 | A kind of ladle top slag for ultra-low-carbon steel deoxidation modification agent and its application method |
| CN106702077B (en) * | 2016-11-18 | 2019-03-05 | 南京钢铁股份有限公司 | A kind of furnace retaining method ensureing the converter high life |
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